Yield:-

Reaction Conditions:

with hydrogenchloride;water at 26.84;

Steps:

Synthesis and growth aspects
l-histidine (99% pure) and hydrochloric acid (HCl) (Merk Product) were taken in 1:2M ratios in excess of double distilled milli pore water as the starting material. The calculated amount of l-histidine was mixed in excess of double distilled milli pore water and the measured amount of HCl was added slowly with stirring to the mixture of water and l-histidine. After the solution become homogeneous (i.e., after continuous stirring for two hours), the solution was filtered to avoid the inclusion of impurities during the stirring and maintained at room temperature (300K) by using a constant temperature bath controlled to an accuracy of ±0.01K. The excess water was allowed to evaporate slowly so as to reach the saturation level of the solution. After the solution has attained the saturation level, well controlled evaporation was maintained to avoid the spurious nucleation. Though the evaporation was controlled carefully, single crystals were grown with two different external morphologies in the same solution. For the first twenty days only the needle like crystals had grown. After twenty days, the secondary nucleation was observed in the same solution and the crystals grown thereafter were in different morphology (bulk in shape) to the previous ones. Several attempts were made by adopting the same procedure and the growth aspects have been confirmed. Seed and grown crystals were carefully harvested from the solution and the photographs of as grown crystals are shown in the Fig. 1. The needle type crystals have been identified as l-histidine and the bulk one as l-histidine hydrochloride monohydrate (LHHC). The measured dimensions are 7×6×30mm³ and 18× 10× 20mm³ for the grown crystals of l-histidine and LHHC respectively.

References:

Anandan;Arivanandhan;Hayakawa;Rajan Babu;Jayavel;Ravi;Bhagavannarayana [Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy,2014,vol. 121,p. 508 - 513]

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